1a.Objectives (from AD-416):
Determine how changes in the amount and state of precipitation will alter nutrient cycling and plant community dynamics in a sagebrush-steppe ecosystem.

1b.Approach (from AD-416):
Experimental research will rely on manipulations of precipitation amount, seasonality, and state (i.e., warming-induced shift from snow to rain) to study the effects of altered climate on.1)plant demographic rates,.2)plant-plant interactions,.3)carbon and nitrogen cycling, and.4)linkages between nutrient cycling and plant performance. Observational studies will focus on plant demographic rates and interactions in the same permanent plots that have been studied since the 1920's.

The experimental and observational results will be used to parametrize and validate demographically mechanistic, multispecies population models. Simulations of these models will project changes in community composition under future climate scenarios, accounting for plant-plant interactions. Results of the nutrient cycling research will be used to evaluate the relative importance of nutrient cycling, soil moisture, and temperature in driving changes in plant demographic rates under altered environmental conditions.

3.Progress Report:

Studies have been initiated to manipulate snowpack and evaluate the.1)effects of reduced snowpack, as would be expected with a warmer climate, on plant community composition;.2)effects of reduced snowpack on soil temperature and moisture fluctuations, carbon release, and nitrogen and phosphorous mineralization-immobilization relationships across a range of autumn soil moisture treatments; and.3)linkages between biogeochemistry and plant community composition. Research plots have been established. Vegetation and other measurements have been made. This is a long-term study, and data will be collected over multiple years. This study contributes to Objective 2 of the related in-house project, "Develop science-based grazing management strategies and decision support systems that can be used to guide managers to maintain or improve the ecological function of western rangelands". The data will be used to improve models for predicting the effects of use and management on plant population in the sagebrush steppe.